The interaction of high-energy radiation (gamma rays, X-rays, and beta particles) with matter produces not only primary impact damage, but also large numbers of non-thermal secondary electrons (˜104 electrons per MeV of decay energy deposited). These lower energy electrons are the main drivers of radiation-induced chemical reactions as well as biological and materials damage, making them arguably the most important species in radiation chemistry. FIG. 1 shows that the majority of the secondary electrons have an energy less than 10 eV. Arumainayagam C R et al. (2010) Surface Science Reports 65:1-44. The dissociative mechanism at energies less than 10 eV is primarily from dissociative electron attachment, in which a short-lived negative ion of the molecule is formed and then dissociates into a radical fragment and an ion fragment. At higher energies electron impact excitation (>6 eV) and ionization (>10 eV) events occur. As is evident from FIG. 1, the plentiful low energy electrons produced from a high energy radioactive decay drive the majority of the chemistry/damage observed at the macro scale.
While macroscopic radioactive decay effects are well understood and have been utilized for decades, single-atom radiochemistry is almost completely unexplored. Nanoscale assembly and atomic-scale imaging of radioactive elements has not been attempted. Verkhoturov et al. observed that the Auger cascade from the electron capture (EC) decay of 55Fe supported on an alkylthiol and fluorocarbon monolayer was the main driver of molecular fragmentation and free ion production. Verkhoturov S V et al. (2001) Phys Rev Lett 87(3):037601.
Huang L et al. (1997) J Chem Phys 107(2):585-91 describes nonradioactive iodine adlayer structures on gold (111Au) films on quartz, as studied using scanning tunneling microscopy (STM).
U.S. Patent Application Publication No. 2013/0302243 (incorporated herein by reference) to Borbély et al. discloses targeted, self-assembled nanoparticles radiolabeled with technetium-99m (99mTc).